This invention generally relates to a coated glass fiber duct board and a method of and apparatus for surface coating the grooves of a glass fiber duct board. More specifically, the invention relates to such a duct board and to an on-line method of and apparatus for applying a surface coating to the grooves of the glass fiber duct board, immediately following the cutting of the grooves in the duct board, to encapsulate the glass fibers exposed and dust created by the groove cutting operation within the surfaces of the grooves.
Dense, rigid, glass fiber duct boards are commonly used to form ductwork in heating, ventilating and air conditioning systems. These duct boards are rigid, strong and self supporting and, after the duct boards are grooved, the duct boards are folded to form the ductwork which has a rectangular transverse cross section.
A somewhat less dense flexible glass fiber blanket is normally used as an internal liner for sheet metal ductwork in heating, ventilating and air conditioning systems. These glass fiber blankets (duct liners) are normally adhered to the sheet metal before the sheet metal is folded to form the ductwork and, due to the flexibility and compressibility of the glass fiber blanket, the duct liner can normally be folded with the sheet metal as the ductwork is formed without the need to cut grooves in the glass fiber blanket to facilitate the folding operation. However, it is contemplated that a dense glass fiber duct board could also be used as a duct liner for sheet metal air ducts in certain applications. Should a glass fiber duct board be used as a liner for sheet metal ductwork, the duct board would be grooved to facilitate the folding operation just as the duct board is grooved when it is used alone to form ductwork.
In addition to serving as an air duct or a duct liner, the glass fiber duct boards function as an insulation: to conserve energy and to maintain the temperature of the air being conveyed within the ductwork within a certain temperature range; to prevent the condensation of moisture on the exterior surfaces of sheet metal ductwork; and to efficiently absorb and control airborne noises.
The surface of the glass fiber duct board forming the interior surface of the air duct is exposed to high velocity air flows. Accordingly, the surface of the duct board that forms the interior surface of the air duct is often coated with a polymeric latex material during the manufacturing operation. The polymeric latex coating forms a tough surface skin on the surface of the duct board that prevents the erosion of glass fibers from the surface by the high velocity air flows passing through the air duct. U.S. Pat. No. 4,990,370, issued on Feb. 5, 1991, to Manville Corporation and entitled "On-Line Surface and Edge Coating of Fiber Glass Duct Liner" discloses a method of and an apparatus for coating glass fiber duct boards and the disclosure of this patent is hereby incorporated herein by reference in its entirety.
However, when the glass fiber duct boards are grooved and formed into ductwork or duct liners at the fabricator's shop or at the job site, the cutting of the grooves in the coated surfaces of the glass fiber duct boards forms uncoated groove surfaces exposing both glass fibers and dust created during the grooving operation. Heretofore, the grooves cut into the glass fiber duct boards at the fabricator's shop or at the job site have remained uncoated leaving the glass fibers and dust in the groove surfaces exposed during the fabrication of the air duct from the duct boards. U.S. Pat. No. 3,875,835, issued on Apr. 8, 1975, to Johns-Manville Corporation, and entitled "Duct Board Cutting Apparatus and Method"; and U.S. Pat. No. 4,781,510, issued on Nov. 1, 1988, to Manville Service Corporation, and entitled "Insulation Board Feeder"; disclose methods of and apparatus for cutting grooves into the surfaces of glass fiber duct boards and the disclosures of these patents are hereby incorporated herein by reference in their entirety.